1. Field of the Invention
The present invention generally relates to improvements in motion and direction sensors and, more particularly, to motion and direction sensors having particular application in End of Train (EOT) railroad telemetry systems.
2. Description of the Prior Art
End of Train (EOT) signalling and monitoring equipment is now widely used, in place of cabooses, to meet operating and safety requirements of railroads. The information monitored by the EOT unit typically includes the air pressure of the brake line, battery condition, marker light operation, and train movement. This information is transmitted to the crew in the locomotive by a battery powered telemetry transmitter. In addition, the EOT unit typically includes a marker light mounted a specific height above the track and having a well defined beam pattern.
The original EOT telemetry systems were one way systems; that is, data was periodically transmitted from the EOT unit to the Head of Train (HOT) unit in the locomotive where the information was displayed. More recently, two way systems have been introduced wherein radio transmissions are also made by the HOT unit to the EOT unit. In one specific application, the EOT unit controls an air valve in the brake line which can be operated by a transmission from the HOT unit.
With the continuing development of EOT units for use in two-way railroad telemetry systems, one goal has been to improve the functionality of the existing motion sensor. This sensor had been reported as not working properly under certain conditions, primarily when operated on smooth rail. In addition, the existing sensor does not report direction of motion, which is now a requirement for certain railroad customers. However, since all railroads require motion reporting to the HOT unit, but only a few require direction reporting, separate motion and direction sensors were developed. Since the motion and direction sensors function independently of each other, this approach minimizes cost, size and complexity for those customers not requiring the direction sensor.